Efficient separation of a mixture into its components is of importance in many industries--for example, in the petroleum, pharmaceutical and chemical industries. Active centrifuges are commonly used to separate species of different molecular weights and densities. In an active centrifuge, centrifugal force is mechanically produced by the rotation of a bowl or some other mechanical device. Passive centrifuges are also known. A cyclone separator is one type of passive centrifuge which is utilized for separation of small solid particles from gases. In a cyclone separator, the mixture is accelerated axially inside a converging cone whereby heavier species such as the solid particles migrate radially outwardly to be extracted at the conical tip, while the lighter species such as the gases collect in the center and are drawn out through an axially-located extraction tube at the inlet end of the device.
The flow in a cyclone separator consists of a double vortex: a larger downward vortex that carries the solid particles near the wall, and a smaller inner upward vortex that carries the gas. This dual vortex flow is quite inefficient and smaller particles are commonly carried out of the device with the gas. Also, a cyclone separator must be vertically oriented to allow gravitational exit of solid particles through its conical bottom. Other separators are known which are uni-directional in operation, i.e., which extract both the lighter species and the heavier species at the end opposite the inlet.